Actuator



C. E. MILLER ACTUATOR Jan. '7, 1947.

Filed Oct. 50. 1944 INVENTOR. CHARLES E. MULLER Patented Jan. 7, 1947ACTUATOR Charles E. Miller, Pasadena, Calif., assignor to BendixAviation Corporation, South Bend, Ind, a corporation of DelawareApplication October 30, 1944, Serial No. 561,141

This invention relates to centrifugal actuators such as may be employedon motor shafts to open or close switches in response to rotation of theshaft above a certain speed.

An object of the invention is to provide a particularly simple,inexpensive, and reliable actuator of the type referred to.

Another object is to provide an actuator the parts of which can be veryeasily and quickly assembled and disassembled.

Still another object is to provide a centrifugal actuator which issubstantially immune to injury or damage by rotation at excessivespeeds.

Other more specific objects and features of the invention will appearfrom the detailed description to follow of a particular embodiment ofthe invention.

Briefly, the invention comprises, in its preferred form, an open-endedcup-shaped body or frame mounted on the end of the shaft to be rotated,and containing an axial shiftable pin which is adapted to engage theswitch plunger or other member to be actuated. When the cup is notrotating, the pin is maintained in an outer, or projected position, by aspring. Adjacent its open end, the cup-shaped frame has diametricallyopposite slots that extend radially and longitudinally and guide a pairof bellcrank levers, the levers being fulcrumed on, a spring wire ringwhich is expanded into an annular groove in the inner surface of thecup-shaped frame. Each bellcrank lever has a long arm extendingsubstantially parallel to th axis of rotation and a short arm extendingradially inwardly into contact with the front end of the axiallyshiftable pin, to oppose the force of the spring. When the device is atrest, there are no centrifugal forces involved, and the spring maintainsthe pin in an outer position in which the long arms of the levers areapproximately parallel to the shaft and are largely contained within theslots in the frame. However, when the shaft bearing the actuator israpidly rotated, the centrifugal force developed in the long arms of thelevers swings them outwardly about their fulcrums, and the short arms ofthe levers force the axially shiftable pin inwardly, overcoming theforce of the spring. The device is most commonly used to actuate acontrolled element of a switch, which controlled element is in contactwith the end of the axially movable pin and, is depressed by the pinwhen the actuator is stationary. When the actuator rotates at suflicientspeed, the pin therein is retracted by the levers, permitting theplunger of the switch to be ejected by a spring 2 Claims. (Cl. 264-15)in the switch mechanism. It is preferable in such devices that theactuator mechanism be completely out of contact with the control switchwhen the actuator is rotating, to eliminate any friction between theparts.

In the drawing:

Fig. 1 is a view showing an actuator in accordance with the inventionmounted on the end of a motor shaft for actuating the plunger of aswitch;

Fig. 2 is a view of the actuator similar to the View of Fig. 1, butshowing the position of the actuator when rotating.

Fig. 3 is a cross section taken substantially in the plane IIIIII ofFig. 1; and

Fig. 4 is a detail section taken in the section IV-IV of Fig. 3.

Referring first to Fig. 1, there is shown a motor In, of any desiredconstruction, having a shaft H on the outer end of which is mounted anactuator 12 in accordance with the present invention, for actuating theplunger l3 of a switch 14.

The actuator l2 comprises a tubular body, or

. frame, I5 having a central bore iii therein. The

rear end of this bore [6 receives the outer end of the motor shaft II,and the body l5 may be secured to the shaft for rotation therewith by apin H.

The bore l6 extends forwardly for a substantial distance beyond the endof the motor shaft II and serves as a guide for a plunger or pin IBhaving a head I9 on its outer or front end. A helical compression spring20 surrounds the pin l8 and is compressed between the body member andthe head I9 of the pin, to constantly urge the latter axially to theright out of the bore l6. Outward movement of the pin [8 by the spring20 is limited by a plurality of bellcrank lever elements 22 which areguided for movement in radial slots l5a provided therefor in the framel5. Each lever element 22 has a long arm 23 extending substantiallyparallel to the axis of the body 15, and a short arm 24, which issubstantially normal to the long arm 23 and extends inwardly intoengagement with the front face of the head l9 of pin 18.

All of the lever elements 22 are fulcrumed on a spring wire ring 25which is positioned in an annular groove 26 formed within the skirtportion of the body l5, each lever element having an aperture 21 forreceiving the wire 25. As best shown in Figs. 3 and 4, the wire ring 25is not continuous but is split and originally shaped to a largerdiameter than the groove 26 in which it is mounted, so that it can bereadily assembled and expands into the groove. The resilience of thewire ring always maintains it in position within the groove because allforces applied to the ring by the lever elements act either outwardly orlongitudinally, never inwardly. One end of the ring is preferably turnedin as indicated at 28 to prevent the ring from shifting in the grooveand releasing the lever elements, although in use there is little or notendency for the ring to shift.

The device can be very readily assembled and disassembled by virtue ofthe fulcrum structure involving the ring 25 in the groove 26. Thus, theprocedure for assembling the parts of the actuator together is to firstplace the helical compression spring 26 about the pin 3 and insert thelatter in the bore 5 8 far enough to fully compress the spring.Thereafter, the lever elements 22 are threaded on to the fulcrum ring25, and the levers and ring are assembled on the body 22 by sliding thelong arms 23 of the lever elements longitudinally into the radial slotsin the body while at the same time squeezing the ring 25 radially (withthe ends of the ring in overlapping relation) to enter the ring into theopen end of the skirt of the body. As soon as the ring has been enteredinto the skirt, it is retained against expansion by the kirt; the ringand the lever elements are then pressed axially until the ring reachesthe groove 26 and snaps into it. Thereafter, the pin I8 will beprevented from escaping from the bore l6 by engagement of the head ofthe pin against the short arms 2 3 of th lever elements.

As shown in Fig. 1, the plunger I3 of the switch I l is engaged by thehead I 9 of pin 13 and slightly depressed thereby, in which position thecontacts of the switch M will be either open or closed according tothedesign of the switch. However, when the actuator is rotated above apredetermined speed, the centrifugal force developed in the long arms 23of the levers 22 throws them outwardly as shown in Fig. 2, in whichposition the short arms 2 of the lever element's depress the pin l8,permitting the plunger iii of the switch to be lifted by a spring (notshown) Within the switch It and close or open the contacts within theswitch, depending upon the construction of the latter. Switches of thetype shown are old and well-known and do not constitute a part of thepresent invention. Preferably, the movement of the pin l8 by the leverelements 22 is sufficient to disengage the head It of the pin from theswitch plunger i3 so that there is no friction therebetween duringrotation of the actuator, after the motor has come up to speed.

As shown in Fig. 2, depression of the pin i8 and outward movement of thelong arms 23 of the lever elements is limited by contact between the endof the neck 39 of the body at the outer end of bore it and the head it.

Various departures from the exact construction shown can be made withoutdeparting from the invention which is to be limited only to the extentset forth in the appended claims. As examples of changes that can bemade, more than two levers 22 may be employed where greater force isrequired. It is desirable, however, in order to produce'a balancedstructure, that the lever arms be symmetrically positioned about theaxis of rotation.

I claim:

1. A centrifugal actuator of the type described comprising: a tubularframe member supported for rotation about its axis and adapted to berotated; a controlled element axially aligned with 7 said axis andsupported for axial movement with respect to said frame member; springmeans urging said controlled member axially in one direction withrespect to said frame member; a plurality of bellcrank lever elementsfulcrumed to said frame member for movement in radial planes, each leverelement having a first arm normally extending approximately parallel tosaid axis and a second arm approximately normal to the first arm andextending inwardly into engagement with said controlled element formoving the latter against the force of said spring means in response tooutward movement of said first arm; said tubular frame member comprisingan annular skirt surrounding said controlled element and said skirthaving an annular groove in its inner surface and having radiallongitudinal slots intersecting said annular groove for slidablyreceiving said lever elements; said lever elements having transversebearing holes therein; and a ring in said groove and extending throughsaid bearing holes in said lever elements for rul crumil'lg said leverelements on said frame member.

2. A centrifugal actuator of the type described comprising: a tubularframe member supported for rotation about its axis and adapted to berotated; a controlled element axially aligned with said axis andsupported for axial movement With respect to said frame member; springmeans urging said controlled member axially in one direction withrespect to said frame member; a plurality of bellcrank lever elementsfulcrumed to said frame member for movement in radial planes, each leverelement having a first arm normally extending approximately parallel tosaid axis and a second arm approximately normal to the first arm andextending inwardly into en a ement with said controlled element formoving the latter against the force of said spring means in response tooutward movement of said first arm; said tubular frame member comprisingan annular skirt surrounding said controlled element and said skirthaving an annular groove in its inner surface and having radiallongitudinal slots intersecting said annular groove for slidablyreceiving said lever elements; said lever elements having transversebearing holes therein; and a split spring wire ring positioned in saidgroove and extending through said bearing holes in said lever elementsfor fulcruming said lever elements on-said frame member; said ring beingoriginally of larger diameter than said annular groove whereby it isresiliently retained in said groove. CHARLES E. 'MILLER.

